Highly efficient tandem organic light-emitting diodes using p-type metal halide copper iodide (CuI)

Abstract

Efficient charge generation is essential for tandem organic light-emitting diode (OLED) devices. In this study, we introduce a p-type copper iodide (CuI) layer within the charge generation layer (CGL) that exhibits high charge generation efficiency in tandem OLED devices. Briefly, CuI is deposited as a thin layer via thermal evaporation technique. X-ray diffraction (XRD) analysis reveals the formation of γ-CuI, and the ultraviolet-visible (UV-Vis) spectral analysis demonstrates outstanding optical transparency (∼95%) of the deposited CuI films in the visible range. The current-voltage (I-V) and capacitance-voltage (C-V) analyses show that the p-type CuI layer is a vital and excellent charge generator and enhances the current density significantly. The tandem OLED device fabricated using Bphen:Liq/CuI/HAT-CN as the CGL results in a substantial 1.9-fold increase in current efficiency compared to the single-unit OLED device, approaching the theoretical two-fold increase. These findings highlight the potential of CuI as a promising p-type material for CGL design in tandem OLED devices.

KEYWORDS:

• CuI
• metal halide
• charge generation layer
• tandem
• OLED

Acknowledgments

This work was supported by the National Research Foundation of Korea (NRF) (NRF-2022R1A4A1028702, NRF-2022M3D1A2083618, and RS-2023-00241971) and the ICT Creative Consilience Program (IITP-2020-0-01821), funded by the Ministry of Science, ICT, and Future Planning.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Ministry of Science, ICT and Future Planning [grant number: IITP-2020-0-01821]; National Research Foundation of Korea [grant number: NRF-2022R1A4A1028702,NRF-2022M3D1A2083618].

Notes on contributors

Kanghoon Kim

Kanghoon Kim: Kanghoon Kim received his B.S. and M.S. degrees from Hanyang University and Sungkyunkwan University, South Korea, in 2014 and 2016, respectively. He joined Samsung Display Company in 2016. He is currently studying a Ph.D. course at Sungkyunkwan University through an academic scholarship program provided by Samsung. His research focuses on tandem structure organic light-emitting diodes.

Jae-In Yoo

Jae-In Yoo: Jae-In Yoo received his B.S. degree from Kyunghee University, South Korea, in 2020. He is currently a Ph.D. student at Sungkyunkwan University. His research focuses on color-tunable light-emitting diodes.

Hyo-Bin Kim

Hyo-Bin Kim: Hyo-Bin Kim received his B.S. and M.S. degrees from Sungkyunkwan University, South Korea, in 2020 and 2022, respectively. He is currently a Ph.D. student at Sungkyunkwan University. His research focuses on the green approach to display field and organic light-emitting diodes.

Sung-Cheon Kang

Sung-Cheon Kang: Sung-Cheon Kang received his B.S. degree from Korea Aerospace University, South Korea, in 2021. He is currently a Ph.D. student at Sungkyunkwan University. His research focuses on color-tunable organic light-emitting diodes.

Jincheol Jang

Jincheol Jang: Jincheol Jang received his M.S. degree from Hanyang University, South Korea in 2014. He is currently a Ph.D. student at Sungkyunkwan University. His research focuses on layer-optimizing light-emitting diodes.

Sundararajan Parani

Sundararajan Parani: Dr. Parani earned his Ph.D. from the Department of Inorganic Chemistry at the University of Madras, India in 2015. Following this, he worked as a postdoctoral researcher at the University of Johannesburg, South Africa until 2021. Currently, he serves as a Research Professor in the Department of Electrical and Electronic Engineering at Sungkyunkwan University, Republic of Korea. His research primarily concentrates on cadmium-free quantum dots including perovskite materials for biomedical, display.

Jang-Kun Song

Jang-Kun Song: Jang-Kun Song received his B.S. and M.S. degrees in physics from Korea University, Seoul, South Korea, in 1994 and 1996, respectively. He also received his Ph.D. degree in electronic engineering from the University of Dublin, Dublin, Ireland, in 2008. He worked in the R&D department of Samsung Electronics Company as a principal engineer from 1996 to 2010. At Samsung, he invented the patterned vertical alignment LCD technology. In 2010, he moved to Sungkyunkwan University, South Korea, where he is currently working as a professor in the School of Electronics and Electrical Engineering. He holds about 240 patents worldwide in display and other technologies. He received the King Sejong Patent Award from the Korean Intellectual Office in 2001.